Predictive Value Of Sting Challenge

RATIONALE: One sting challenge (SC) with no systemic reaction (SR) can still be followed by SR to a second SC in 15-20% cases. Our aim was to determine the outcome of stings occurring in the field (FS) in the years after SC was performed. METHODS: SC was performed in 233 patients between 1997-2004. During the study we inquire annually about the details of any FS. We recently surveyed all patients for information on FS that occurred after the initial SC. RESULTS: The overall frequency of systemic reactions to the SC was 69/233 patients (30%). Reaction occurred on initial SC in 52/233 (22%), and on second SC in 17 of 86 initial non-reactors (20%). Information on FS was available for 116 patients: 30 had had a SR to the SC (reactors) and 86 had not (non-reactors). Among the reactors, 10 reported FS and 3 (30%) had a SR. Among the non-reactors, 28 reported FS and 1 (3.5%) had a SR. Of these 28, 15 had had one SC and 13 had >=2 SC. The reaction rate was significantly greater in the SC reactors (p < 0.01). CONCLUSIONS: Patients who did not react to SC had a low risk of reaction to FS, but sequential (same-summer) stings may still cause a reaction. Reactions still may occur with a second SC with a known insect. Those who do react to SC continue to have the same 30% risk of reaction to FS.